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Green Building Guide

Insulation

One of the best ways to
save money on energy bills is to insulate your home. Insulation is
like a barrier, preventing heat passing in and out of the
house.

By reducing heat flow you can maintain a comfortable temperature
inside, regardless of the temperature outside.

In winter, once the dwelling has been heated to a comfortable
level, it will stay that way with less energy input than an
uninsulated home.

In summer the insulated home will take longer to heat up, and
air conditioners will need less energy for cooling.

There are two main types of insulation: bulk and reflective.
Bulk insulation comes in many shapes, thicknesses and materials and
is primarily used in ceilings and sometimes in walls.

The most common bulk insulation material is mineral wool or
glass fibre. Other materials include recycled and virgin polyester,
wool and cellulose fibre. Bulk insulation stops heat flow by
trapping air in small air pockets.

Reflective insulation resists radiant heat by reflecting or not
emitting heat. It is usually shiny aluminium foil laminated onto
paper or plastic. Reflective insulation needs a layer of air
between its shiny reflective side and the roof or wall cladding.
The insulation's effectiveness can also decrease if it becomes
dirty or dusty.

When looking for insulation you will come across the term
'R-value'. The R-value measures the product's ability to insulate,
or resist heat transfer. The higher the R-value, the greater the
level of insulation. A batt with an installed R-value of R1.5 will
let more heat through than an R2.6 batt.

Another insulation term you may hear is U-value, which is the
opposite of R-value. The U-value relates to how well the material
transfers heat. With U-values, the lower the number the better.
Bulk insulation products come with one R-value for a given
thickness. Reflective insulation's R-value depends on where and how
the insulation is installed.

The type and level of insulation you need for your home varies
on where you live, the building materials used for your house and
whether you will be using additional heating or cooling. A home in
an alpine region would want to stop heat flowing out in winter and
prevent heat coming in during summer. These homes benefit from
reflective insulation under the roof, floors and in walls, and bulk
insulation in the ceiling.

Most common building materials have little insulating value, but
there are some other options available. Aerated concrete blocks,
fibre reinforced gypsum, hollow expanded polystyrene blocks,
rendered strawbales and rendered polystyrene sheets can insulate
your home with little or no need for additional insulation.

When installing insulation make sure there are no gaps as this
decreases the effectiveness of insulation. This is especially a
problem with halogen downlights in ceilings.

Finally, when choosing insulation compare the environmental
benefits of different products. Ask how much of the product is made
from recycled materials and how easily the product can be recycled.
For example some products are made from 80 per cent recycled
plastic drink bottles or 100 per cent recycled paper.

The higher the bushfire risk, the greater the caution required
in selecting appropriate insulation products. Some insulation
products are non-combustible and non-flamable (e.g. Rockwool) and
so are recommended to seal roof/wall junctions for example.

Other products such as reflective foil roof sarking are required
to stop embers under tiles and metal sheet roofs. Depending on your
Bushfire Attack level (BAL), some insulation products (e.g.
polystyrene, polyurethane blocks and panels, PVC) may not be
suitable because they could be exposed to heat or flame in external
walls.